import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {

        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        int p = sc.nextInt();
        int q = sc.nextInt();
        
        int ans = 0;
        while(n > 0){
            int season = q;
            for(int i = 1 ; i <= 12 ; i++){
                if(i == p){
                    while(season > 0){
                        n -= 2 * m;
                        ans++;
                        season--;
                        if(n <= 0){
                            break;
                        }
                    }
                    i += q - season - 1;
                } else {
                    n -= m;
                    ans++;
                }
                if(n <= 0){
                    break;
                }
            }
            //System.out.println(n);
        }
        
        System.out.println(ans);

    }

}